Carbamazepine (CBZ) is a drug that is frequently prescribed in treatment of epilepsy and bipolar disorder. HLA-B*15:02 is strongly associated with carbamazepine-induced life-threatening inflammatory adverse reactions in skin and mucous membrane (Chung et al., Medical genetics: a marker for Stevens-Johnson syndrome, Nature, 2004, 428(6982): p. 486; Chen et al., Carbamazepine-induced toxic effects and HLA-B*15:02 screening in Taiwan, N Engl J Med, 2011, 364(12): pp. 1126-33). See also www.fda.gov/Drugs/DrugSafety/PostmarketDrugSafetyInformationforPatientsandProviders/ucm 124718.htm. Thus, HLA-B*15:02 screening is warranted in patients requiring carbamazepine therapy (Tegretol® and Tegretol®-XR prescribing information: FDA approved labeling. 2014). Currently, the detection of HLA-B*15:02 through HLA typing is feasible but technically challenging due to the highly polymorphic and homologous nature of all HLA-B haplotypes. Current HLA typing methods have limitations in resolution, accuracy, price, and/or convenience that prevent them from wide use for HLA-B*15:02 screening.
Briefly, there are four major approaches for HLA-B*15:02 detection currently available:                (1) Direct sequencing methods—e.g., Sanger sequencing or next-generation sequencing (NGS)—are the most accurate options, but they are time-consuming, expensive, and also requiring special expertise to analyze the data;        (2) Sequence-specific oligonucleotide probe hybridization (SSOP) has high sensitivity and specificity, but it also has many disadvantages including complex processing and low resolution;        (3) Sequence-specific PCR (SSP-PCR), for example, the commercially available Pharmigene PG15:02 Detection Kit (U.S. Pat. No. 7,470,513), is less expensive and easier to process, but it is low throughput, and has low specificity owing to cross-reactions; and        (4) Tagging SNP method, in particular a two-SNP haplotype consisting of the minor alleles of rs2844682 and rs3909184, has been reported to tag the HLA-B*15:02 allele in 45 unrelated individuals from the HapMap (International HapMap, C., The International HapMap Project. Nature, 2003, 426(6968): pp. 789-96) population of Han Chinese in Beijing, China (CHB) (de Bakker et al., A high-resolution HLA and SNP haplotype map for disease association studies in the extended human MHC. Nat Genet, 2006, 38(10): pp. 1166-72). However, further testing has demonstrated these two SNPs have very poor accuracy (with ˜6% sensitivity) to detect HLA-B*15:02 (Zhu, G. D., et al., Genotypes at rs2844682 and rs3909184 have no clinical value in identifying HLA-B*15:02 carriers. Eur J Clin Pharmacol, 2015).        
Thus, in light of the potential for life-threatening adverse reactions caused by carbamazepine and related drugs, there is an urgent need for an accurate, high-throughput, and cost-effective assay for HLA-B*15:02 screening. In particular, an ideal assay should produce no false negatives. Such an assay would be highly valuable and immediately desired in clinical practice.